Specialize string equality for various string classes. Implement intrinsics for string equal…

runtime/lib/string_patch.dart

Index: runtime/lib/string_patch.dart
===================================================================
--- runtime/lib/string_patch.dart	(revision 29225)
+++ runtime/lib/string_patch.dart	(working copy)
@@ -89,9 +89,16 @@
       // TODO(5413632): Compare hash codes when both are present.
       return false;
     }
-    return this.compareTo(other) == 0;
+    final len = this.length;
+    for (int i = 0; i < len; i++) {
+      if (this.codeUnitAt(i) != other.codeUnitAt(i)) {
+        return false;
+      }
+    }
+    return true;
   }
 
+
   int compareTo(String other) {
     int thisLength = this.length;
     int otherLength = other.length;
@@ -523,6 +530,10 @@
     return _StringBase._isOneByteWhitespace(codePoint);
   }
 
+  bool operator ==(Object other) {
+    return super == other;
+  }
+
   String _substringUncheckedNative(int startIndex, int endIndex)
       native "OneByteString_substringUnchecked";
 
@@ -575,6 +586,10 @@
   bool _isWhitespace(int codePoint) {
     return _StringBase._isTwoByteWhitespace(codePoint);
   }
+
+  bool operator ==(Object other) {
+    return super == other;
+  }
 }
 
 
@@ -587,6 +602,10 @@
   bool _isWhitespace(int codePoint) {
     return _StringBase._isOneByteWhitespace(codePoint);
   }
+
+  bool operator ==(Object other) {
+    return super == other;
+  }
 }
 
 
@@ -599,6 +618,10 @@
   bool _isWhitespace(int codePoint) {
     return _StringBase._isTwoByteWhitespace(codePoint);
   }
+
+  bool operator ==(Object other) {
+    return super == other;
+  }
 }